Clostridial toxin derivatives and methods for treating pain

ABSTRACT

Agents for treating pain, methods for producing the agents and methods for treating pain by administration to a patient of a therapeutically effective amount of the agent. The agent can include a clostridial neurotoxin, or a component or fragment or derivative thereof, attached to a targeting moiety, wherein the targeting moiety is selected from a group consisting of transmission compounds which can be released from neurons upon the transmission of pain signals by the neurons, and compounds substantially similar to the transmission compounds.

This application is a continuation and claims priority pursuant to 35U.S.C. §120 to U.S. patent application Ser. No. 09/489,667, filed Jan.19, 2000, which is hereby incorporated by reference in its entirety.

BACKGROUND

The present invention relates to compositions and methods for treatingpain. In particular, the present invention relates to Clostridial toxinderivatives, methods for making the Clostridial toxin derivatives andmethods for treating pain using the Clostridial toxin derivatives.

Many, if not most aliments of the body cause pain. The causes of paincan include inflammation, muscle spasm and the onset of a neuropathicevent or syndrome. Inflammatory pain can occur when tissue is damaged,as can result from surgery or due to an adverse physical, chemical orthermal event or to infection by a biologic agent. Spasticity or musclespasm can be a serious complication of trauma to the spinal cord orother disorders that create damage within the spinal cord. Muscle spasmis often accompanied by pain. The pain experienced during a muscle spasmcan result from the direct effect of the muscle spasm stimulatingmechanosensitive pain receptors or from the indirect effect of the spasmcompressing blood vessels and causing ischemia. Since the spasmincreases the rate of metabolism in the affected muscle tissue, therelative ischemia becomes greater creating thereby conditions for therelease of pain inducing substances. Neuropathic pain is a persistent orchronic pain syndrome that can result from damage to the nervous system,the peripheral nerves, the dorsal root ganglion or dorsal root, or tothe central nervous system.

Neuropathic pain syndromes include allodynia, various neuralgias such aspost herpetic neuralgia and trigeminal neuralgia, phantom pain, andcomplex regional pain syndromes, such as reflex sympathetic dystrophyand causalgia. Causalgia is characterized by spontaneous burning paincombined with hyperalgesia and allodynia.

Pain can be experienced when the free nerve endings which constitute thepain receptors in the skin as well as in certain internal tissues aresubjected to mechanical, thermal or chemical stimuli. The pain receptorstransmit signals along afferent neurons into the central nervous systemand thence to the brain.

The transduction of sensory signals, such as pain signals, from theperiphery to sensation itself is achieved by a multi-neuronal pathwayand the information processing centers of the brain. The first nervecells of the pathway involved in the transmission of sensory stimuli arecalled primary sensory afferents. The cell bodies for the primarysensory afferents from the head and some of the internal organs residein various ganglia associated with the cranial nerves, particularly thetrigeminal nuclei and the nucleus of the solitary tract. The cell bodiesfor the primary sensory afferents for the remainder of the body lie inthe dorsal root ganglia of the spinal column. The primary sensoryafferents and their processes have been classified histologically; thecell bodies fall into two classes: A-types are large (60-120 micrometerin diameter) while B-types are smaller (14-30 micrometer) and morenumerous. Similarly the processes fall into two categories: C-fiberslack the myelin sheath that A-fibers possess. A-fibers can be furthersub-divided into A beta-fibers, that are large diameters with welldeveloped myelin, and A delta-fibers, that are thinner with less welldeveloped myelin. It is generally believed that A beta-fibers arise fromA-type cell bodies and that A delta- and C-fibers arise from B-type cellbodies.

After the activation of the primary sensory afferents the next step inthe transduction of sensory signals is the activation of the projectionneurons, which carry the signal, via the spinothalamic tract, to higherparts of the central nervous system such as the thalamic nuclei. Thecell bodies of these neurons (other than those related to the cranialnerves) are located in the dorsal horn of the spinal cord. This is alsowhere the synapses between the primary afferents and the projectionneurons are located. The dorsal horn is organized into a series oflaminae that are stacked, with lamina I being most dorsal followed bylamina II, etc. The different classes of primary afferents make synapsesin different laminae. For cutaneous primary afferents, C-fibers makesynapses in laminae I and II, A delta-fibers in laminae I, II, and V,and A beta-fibers in laminae III, IV, and V. Deeper laminae (V-VII, X)are thought to be involved in the sensory pathways arriving from deepertissues such as muscles and the viscera.

The predominant neurotransmitters at the synapses between primaryafferents and projection neurons are substance P, glutamate,calcitonin-gene related peptide (CGRP) and neuropeptide Y. Theefficiency of transmission of these synapses can be altered viadescending pathways and by local interneurons in the spinal cord. Thesemodulatory neurons release a number of mediators that are eitherinhibitory (e.g. opioid peptides, glycine) or excitatory (e.g. nitricoxide, cholecystokinin), to provide a mechanism for enhancing orreducing awareness of sensations.

Effective pain alleviating drugs are needed. It is known thatintraspinal administration of opioids, such as morphine and fentanyl canalleviate pain. See e.g. Gianno, J., et al., Intrathecal Drug Therapyfor Spasticity and Pain, Springer-Verlag (1996) (which publication isincorporated herein by reference in its entirety). Unfortunately,current drugs used in intraspinal, or intrathecal, injections typicallyhave only short lived antinociceptive effects. As a result, these drugshave to be frequently administered, such as by the aid of a pump forcontinuous infusion. For example, one frequently used pump is theSynchroMed® Infusion System, a programmable, implanted pump availablefrom Medtronic, Inc., of Minneapolis, Minn. However, complications canarise due to the required surgical implantation procedure for the use ofthe pump and the known intrathecally administered drugs for pain, suchas opioids, have the disadvantages of dependency and potentialrespiratory depression.

Longer acting analgesics are also known, for example, blocks by phenolinjection. However, such treatments raise a considerable risk ofirreversible functional impairment.

Intrathecal administration of botulinum toxin type B to mice to treatthermal hyperalgesia is known. Br. J. Pharmacol 1999; 127(2):449-456.Additionally, it has been reported (Science, 1999; 286:1558-1561)(“Nichols et al.”) that intrathecal injection of a cytotoxicsaporin-substance P (saporin can be abbreviated as “SAP” and substance Pcan be abbreviated as “SP”) conjugate (which can be abbreviated asSAP-SP) results in a reduction of thermal hyperalgesia and mechanicalallodynia.

As discussed Nichols et al, supra, spinothalamic and spinoparabrachialneurons are involved in the ascending conduction of acute noxiousstimuli. Apparently, these neurons are projection neurons can betargeted by substance P. When a conjugate of the ribosome-inactivatingprotein saporin and SP was intrathecally infused into the spinal cord,the SAP-SP conjugate is stated to have specifically concentrated in theprojection neurons, apparently because these neurons express cellsurface receptors for substance P (a substance P receptor can beabbreviated as “SPR”). Unfortunately, the SAP-SP targeted neurons arekilled by the SAP.

Although SAP-SP is specific for projection neurons because projectionneurons appear to express the SPR, an intrathecal injection of SAP-SPmay cause necrosis of other neurons through non-specific or low affinitySAP-SP neuronal interactions. For example, SAP-SP may interact with andcause motor neurons cell death. Since motor neurons and most otherneurons in the spinal cord do not regenerate, it is contraindicated touse SAP-SP in humans, unless destruction of the neurons with theresulting in permanent disablement, and for example, paralysis, is adesired end result. Clearly it would be desirable to be able to treatpain, including chronic pain, without causing necrosis and irreversibleloss of the neurons treated.

Botulinum Toxin

The anaerobic, gram positive bacterium Clostridium botulinum produces apotent polypeptide neurotoxin, botulinum toxin, which causes aneuroparalytic illness in humans and animals referred to as botulism.The spores of Clostridium botulinum are found in soil and can grow inimproperly sterilized and sealed food containers of home basedcanneries, which are the cause of many of the cases of botulism. Theeffects of botulism typically appear 18 to 36 hours after eating thefoodstuffs infected with a Clostridium botulinum culture or spores. Thebotulinum toxin can apparently pass unattenuated through the lining ofthe gut and attack peripheral motor neurons. Symptoms of botulinum toxinintoxication can progress from difficulty walking, swallowing, andspeaking to paralysis of the respiratory muscles and death.

Botulinum toxin type A is the most lethal natural biological agent knownto man. About 50 picograms of botulinum toxin (purified neurotoxincomplex) type A is a LD₅₀ in mice. One unit (U) of botulinum toxin isdefined as the LD₅₀ upon intraperitoneal injection into female SwissWebster mice weighing 18-20 grams each. Seven immunologically distinctbotulinum neurotoxins have been characterized, these being respectivelybotulinum neurotoxin serotypes A, B, C₁, D, E, F and G each of which isdistinguished by neutralization with type-specific antibodies. Thedifferent serotypes of botulinum toxin vary in the animal species thatthey affect and in the severity and duration of the paralysis theyevoke. For example, it has been determined that botulinum toxin type Ais 500 times more potent, as measured by the rate of paralysis producedin the rat, than is botulinum toxin type B. Additionally, botulinumtoxin type B has been determined to be non-toxic in primates at a doseof 480 U/kg which is about 12 times the primate LD₅₀ for botulinum toxintype A. Botulinum toxin apparently binds with high affinity tocholinergic motor neurons, is translocated into the neuron and blocksthe release of acetylcholine.

Botulinum toxins have been used in clinical settings for the treatmentof neuromuscular disorders characterized by hyperactive skeletalmuscles. Botulinum toxin type A has been approved by the U.S. Food andDrug Administration for the treatment of blepharospasm, strabismus andhemifacial spasm. Non-type A botulinum toxin serotypes apparently have alower potency and/or a shorter duration of activity as compared tobotulinum toxin type A. Clinical effects of peripheral intramuscularbotulinum toxin type A are usually seen within one week of injection.The typical duration of symptomatic relief from a single intramuscularinjection of botulinum toxin type A averages about three months.

Although all the botulinum toxins serotypes apparently inhibit releaseof the neurotransmitter acetylcholine at the neuromuscular junction,they do so by affecting different neurosecretory proteins and/orcleaving these proteins at different sites. For example, botulinum typesA and E both cleave the 25 kiloDalton (kD) synaptosomal associatedprotein (SNAP-25), but they target different amino acid sequences withinthis protein. Botulinum toxin types B, D, F and G act onvesicle-associated protein (VAMP, also called synaptobrevin), with eachserotype cleaving the protein at a different site. Finally, botulinumtoxin type C₁ has been shown to cleave both syntaxin and SNAP-25. Thesedifferences in mechanism of action may affect the relative potencyand/or duration of action of the various botulinum toxin serotypes.

Regardless of serotype, the molecular mechanism of toxin intoxicationappears to be similar and to involve at least three steps or stages. Inthe first step of the process, the toxin binds to the presynapticmembrane of the target neuron through a specific interaction between theH chain and a cell surface receptor; the receptor is thought to bedifferent for each type of botulinum toxin and for tetanus toxin. Thecarboxyl end segment of the H chain, H_(c), appears to be important fortargeting of the toxin to the cell surface.

In the second step, the toxin crosses the plasma membrane of thepoisoned cell. The toxin is first engulfed by the cell throughreceptor-mediated endocytosis, and an endosome containing the toxin isformed. The toxin then escapes the endosome into the cytoplasm of thecell. This last step is thought to be mediated by the amino end segmentof the H chain, H_(N), which triggers a conformational change of thetoxin in response to a pH of about 5.5 or lower. Endosomes are known topossess a proton pump which decreases intra endosomal pH. Theconformational shift exposes hydrophobic residues in the toxin, whichpermits the toxin to embed itself in the endosomal membrane. The toxinthen translocates through the endosomal membrane into the cytosol.

The last step of the mechanism of botulinum toxin activity appears toinvolve reduction of the disulfide bond joining the H and L chain. Theentire toxic activity of botulinum and tetanus toxins is contained inthe L chain of the holotoxin; the L chain is a zinc (Zn++) endopeptidasewhich selectively cleaves proteins essential for recognition and dockingof neurotransmitter-containing vesicles with the cytoplasmic surface ofthe plasma membrane, and fusion of the vesicles with the plasma membranetetanus neurotoxin, botulinum toxin/B/D,/F, and/G cause degradation ofsynaptobrevin (also called vesicle-associated membrane protein (VAMP)),a synaptosomal membrane protein. Most of the VAMP present at thecytosolic surface of the synaptic vesicle is removed as a result of anyone of these cleavage events. Each toxin specifically cleaves adifferent bond.

The molecular weight of the botulinum toxin protein molecule, for allseven of the known botulinum toxin serotypes, is about 150 kD.Interestingly, the botulinum toxins are released by Clostridialbacterium as complexes comprising the 150 kD botulinum toxin proteinmolecule along with associated non-toxin proteins. Thus, the botulinumtoxin type A complex can be produced by Clostridial bacterium as 900 kD,500 kD and 300 kD forms. Botulinum toxin types B and C, is apparentlyproduced as only a 500 kD complex. Botulinum toxin type D is produced asboth 300 kD and 500 kD complexes. Finally, botulinum toxin types E and Fare produced as only approximately 300 kD complexes. The complexes (i.e.molecular weight greater than about 150 kD) are believed to contain anon-toxin hemaglutinin protein and a non-toxin and non-toxicnonhemaglutinin protein. These two non-toxin proteins (which along withthe botulinum toxin molecule comprise the relevant neurotoxin complex)may act to provide stability against denaturation to the botulinum toxinmolecule and protection against digestive acids when toxin is ingested.Additionally, it is possible that the larger (greater than about 150 kDmolecular weight) botulinum toxin complexes may result in a slower rateof diffusion of the botulinum toxin away from a site of intramuscularinjection of a botulinum toxin complex.

In vitro studies have indicated that botulinum toxin inhibits potassiumcation induced release of both acetylcholine and norepinephrine fromprimary cell cultures of brainstem tissue. Additionally, it has beenreported that botulinum toxin inhibits the evoked release of bothglycine and glutamate in primary cultures of spinal cord neurons andthat in brain synaptosome preparations botulinum toxin inhibits therelease of each of the neurotransmitters acetylcholine, dopamine,norepinephrine, CGRP and glutamate.

Botulinum toxin type A can be obtained by establishing and growingcultures of Clostridium botulinum in a fermenter and then harvesting andpurifying the fermented mixture in accordance with known procedures. Allthe botulinum toxin serotypes are initially synthesized as inactivesingle chain proteins which must be cleaved or nicked by proteases tobecome neuroactive. The bacterial strains that make botulinum toxinserotypes A and G possess endogenous proteases and serotypes A and G cantherefore be recovered from bacterial cultures in predominantly theiractive form. In contrast, botulinum toxin serotypes C₁, D and E aresynthesized by nonproteolytic strains and are therefore typicallyunactivated when recovered from culture. Serotypes B and F are producedby both proteolytic and nonproteolytic strains and therefore can berecovered in either the active or inactive form. However, even theproteolytic strains that produce, for example, the botulinum toxin typeB serotype only cleave a portion of the toxin produced. The exactproportion of nicked to unnicked molecules depends on the length ofincubation and the temperature of the culture. Therefore, a certainpercentage of any preparation of, for example, the botulinum toxin typeB toxin is likely to be inactive, possibly accounting for the knownsignificantly lower potency of botulinum toxin type B as compared tobotulinum toxin type A. The presence of inactive botulinum toxinmolecules in a clinical preparation will contribute to the overallprotein load of the preparation, which has been linked to increasedantigenicity, without contributing to its clinical efficacy.Additionally, it is known that botulinum toxin type B has, uponintramuscular injection, a shorter duration of activity and is also lesspotent than botulinum toxin type A at the same dose level.

It has been reported that botulinum toxin type A has been used inclinical settings as follows:

-   -   (1) about 75-125 units of BOTOX®¹ per intramuscular injection        (multiple muscles) to treat cervical dystonia;        ¹Available from Allergan, Inc., of Irvine, Calif. under the        tradename BOTOX®.    -   (2) 5-10 units of BOTOX® per intramuscular injection to treat        glabellar lines (brow furrows) (5 units injected intramuscularly        into the procerus muscle and 10 units injected intramuscularly        into each corrugator supercilii muscle);    -   (3) about 30-80 units of BOTOX® to treat constipation by        intrasphincter injection of the puborectalis muscle;    -   (4) about 1-5 units per muscle of intramuscularly injected        BOTOX® to treat blepharospasm by injecting the lateral        pre-tarsal orbicularis oculi muscle of the upper lid and the        lateral pre-tarsal orbicularis oculi of the lower lid.    -   (5) to treat strabismus, extraocular muscles have been injected        intramuscularly with between about 1-5 units of BOTOX®, the        amount injected varying based upon both the size of the muscle        to be injected and the extent of muscle paralysis desired (i.e.        amount of diopter correction desired).    -   (6) to treat upper limb spasticity following stroke by        intramuscular injections of BOTOX® into five different upper        limb flexor muscles, as follows:        -   (a) flexor digitorum profundus: 7.5 U to 30 U        -   (b) flexor digitorum sublimus: 7.5 U to 30 U        -   (c) flexor carpi ulnaris: 10 U to 40 U        -   (d) flexor carpi radialis: 15 U to 60 U        -   (e) biceps brachii: 50 U to 200 U. Each of the five            indicated muscles has been injected at the same treatment            session, so that the patient receives from 90 U to 360 U of            upper limb flexor muscle BOTOX® by intramuscular injection            at each treatment session.

The success of botulinum toxin type A to treat a variety of clinicalconditions has led to interest in other botulinum toxin serotypes. Astudy of two commercially available botulinum type A preparations(BOTOX® and Dysport®) and preparations of botulinum toxins type B and F(both obtained from Wako Chemicals, Japan) has been carried out todetermine local muscle weakening efficacy, safety and antigenicpotential. Botulinum toxin preparations were injected into the head ofthe right gastrocnemius muscle (0.5 to 200.0 units/kg) and muscleweakness was assessed using the mouse digit abduction scoring assay(DAS). ED₅₀ values were calculated from dose response curves. Additionalmice were given intramuscular injections to determine LD₅₀ doses. Thetherapeutic index was calculated as LD₅₀/ED₅₀. Separate groups of micereceived hind limb injections of BOTOX® (5.0 to 10.0 units/kg) orbotulinum toxin type B (50.0 to 400.0 units/kg), and were tested formuscle weakness and increased water consumption, the later being aputative model for dry mouth. Antigenic potential was assessed bymonthly intramuscular injections in rabbits (1.5 or 6.5 ng/kg forbotulinum toxin type B or 0.15 ng/kg for BOTOX®). Peak muscle weaknessand duration were dose related for all serotypes. DAS ED₅₀ values(units/kg) were as follows: BOTOX®: 6.7, Dysport®: 24.7, botulinum toxintype B: 27.0 to 244.0, botulinum toxin type F: 4.3. BOTOX® had a longerduration of action than botulinum toxin type B or botulinum toxin typeF. Therapeutic index values were as follows: BOTOX®: 10.5, Dysport®:6.3, botulinum toxin type B: 3.2. Water consumption was greater in miceinjected with botulinum toxin type B than with BOTOX®, althoughbotulinum toxin type B was less effective at weakening muscles. Afterfour months of injections 2 of 4 (where treated with 1.5 ng/kg) and 4 of4 (where treated with 6.5 ng/kg) rabbits developed antibodies againstbotulinum toxin type B. In a separate study, 0 of 9 BOTOX® treatedrabbits demonstrated antibodies against botulinum toxin type A. DASresults indicate relative peak potencies of botulinum toxin type A beingequal to botulinum toxin type F, and botulinum toxin type F beinggreater than botulinum toxin type B. With regard to duration of effect,botulinum toxin type A was greater than botulinum toxin type B, andbotulinum toxin type B duration of effect was greater than botulinumtoxin type F. As shown by the therapeutic index values, the twocommercial preparations of botulinum toxin type A (BOTOX® and Dysport®)are different. The increased water consumption behavior observedfollowing hind limb injection of botulinum toxin type B indicates thatclinically significant amounts of this serotype entered the murinesystemic circulation. The results also indicate that in order to achieveefficacy comparable to botulinum toxin type A, it is necessary toincrease doses of the other serotypes examined. Increased dosage cancomprise safety. Furthermore, in rabbits, type B was more antigenic thanwas BOTOX®, possibly because of the higher protein load injected toachieve an effective dose of botulinum toxin type B.

The tetanus neurotoxin acts mainly in the central nervous system, whilebotulinum neurotoxin acts at the neuromuscular junction; both act byinhibiting acetylcholine release from the axon of the affected neuroninto the synapse, resulting in paralysis. The effect of intoxication onthe affected neuron is long-lasting and until recently has been thoughtto be irreversible. The tetanus neurotoxin is known to exist in oneimmunologically distinct type

Acetylcholine

Typically only a single type of small molecule neurotransmitter isreleased by each type of neuron in the mammalian nervous system. Theneurotransmitter acetylcholine is secreted by neurons in many areas ofthe brain, but specifically by the large pyramidal cells of the motorcortex, by several different neurons in the basal ganglia, by the motorneurons that innervate the skeletal muscles, by the preganglionicneurons of the autonomic nervous system (both sympathetic andparasympathetic), by the postganglionic neurons of the parasympatheticnervous system, and by some of the postganglionic neurons of thesympathetic nervous system. Essentially, only the postganglionicsympathetic nerve fibers to the sweat glands, the piloerector musclesand a few blood vessels are cholinergic and most of the postganglionicneurons of the sympathetic nervous system secret the neurotransmitternorepinephine. In most instances acetylcholine has an excitatory effect.However, acetylcholine is known to have inhibitory effects at some ofthe peripheral parasympathetic nerve endings, such as inhibition of theheart by the vagal nerve.

The efferent signals of the autonomic nervous system are transmitted tothe body through either the sympathetic nervous system or theparasympathetic nervous system. The preganglionic neurons of thesympathetic nervous system extend from preganglionic sympathetic neuroncell bodies located in the intermediolateral horn of the spinal cord.The preganglionic sympathetic nerve fibers, extending from the cellbody, synapse with postganglionic neurons located in either aparavertebral sympathetic ganglion or in a prevertebral ganglion. Since,the preganglionic neurons of both the sympathetic and parasympatheticnervous system are cholinergic, application of acetylcholine to theganglia will excite both sympathetic and parasympathetic postganglionicneurons.

Acetylcholine activates two types of receptors, muscarinic and nicotinicreceptors. The muscarinic receptors are found in all effector cellsstimulated by the postganglionic neurons of the parasympathetic nervoussystem, as well as in those stimulated by the postganglionic cholinergicneurons of the sympathetic nervous system. The nicotinic receptors arefound in the synapses between the preganglionic and postganglionicneurons of both the sympathetic and parasympathetic. The nicotinicreceptors are also present in many membranes of skeletal muscle fibersat the neuromuscular junction.

Acetylcholine is released from cholinergic neurons when small, clear,intracellular vesicles fuse with the presynaptic neuronal cell membrane.A wide variety of non-neuronal secretory cells, such as, adrenal medulla(as well as the PC12 cell line) and pancreatic islet cells releasecatecholamines and insulin, respectively, from large dense-corevesicles. The PC12 cell line is a clone of rat pheochromocytoma cellsextensively used as a tissue culture model for studies ofsympathoadrenal development. Botulinum toxin inhibits the release ofboth types of compounds from both types of cells in vitro, permeabilized(as by electroporation) or by direct injection of the toxin into thedenervated cell. Botulinum toxin is also known to block release of theneurotransmitter glutamate from cortical synaptosomes cell cultures.

U.S. Pat. No. 5,989,545 (“Foster et al.”) (incorporated herein byreference in its entirety) discusses conjugating clostridial neurotoxinsto targeting moieties in order to direct the inhibitory effect ofclostridial neurotoxins toward primary sensory afferent neurons. Thus,the mechanism by which the agents disclosed by Foster et al alleviatepain is as follows: the targeting moieties of the agents, for examplethe growth factors, bind to receptor sites on the sensory afferent nerveterminals, for example the growth factor receptors, in the spinal cord;then, the clostridial neurotoxins, along with the conjugated targetingmoieties, translocate into the nerve terminal and inhibit the release ofone or more transmitters involved in the signaling of pain, and therebyalleviate pain.

Unlike SAP-SP, the clostridial-targeting moiety conjugates disclosed byFoster et al do not appear to be cytotoxic. Despite their superiority tothe SAP-SP in that they are non-cytotoxic, they are still inadequate aspain alleviating agents because they lack the specificity for treatingpain. More particularly, the Foster et al's targeting moieties intendedfor primary sensory afferent neurons are non-specific.

Thus, the agents disclosed by Foster et al are non-specific becausetheir targeting moieties are not known to bind to receptors specificallyand to primarily localize to primary sensory afferent nerve terminals.Therefore, the targeting moieties disclosed by Foster et al. may readilybind to receptors on neuronal terminals, or neurons, that are notprimary sensory afferent synaptic terminals. For example, the targetingmoiety comprising nerve growth factor disclosed by Foster may readilybind to receptors on nerve terminals and neurons other than thereceptors on the primary sensory afferent nerve terminals, because nervegrowth factor receptors are found on most neurons. As such, theclostridial neurotoxin conjugate disclosed by Foster et al may bind toone of these other neurons, for example the neurons involved in thesympathetic pathway, translocate into their cytosol, inhibit the releaseof their neurotransmitters, and thereby inhibiting their functions. Suchrandom, non-specific inhibition may cause undesirable side effectsduring the treatment of pain.

Similarly, bradykinin, another targeting moieties disclosed by Foster etal, have been shown to have high density concentration in the motorneurons of the ventral horn in the spinal cord. (See Lopes et al,Neuroscience 78(2):481-497, the content of which is incorporated in itsentirety herein by reference.) Agents disclosed by Foster et al whichbear bradykinins as targeting moieties will significantly interact andinterfere with motor functions when the agents are injectedintraspinally to treat pain.

Also, the opioid receptor binding targeting moieties disclosed by Fosteret al, for example, methionine-enkephalin, are non-specific with respectto directing the clostridial neurotoxin to the primary sensory afferentnerve terminal. Kandel et al, Principles of Neural Science, thirdedition, page 395, (1991), indicated that opioid receptors are widelydistributed throughout the central nervous system, suggesting thatopioid receptors, when activated, modulate physiological functions otherthan pain. Therefore, the clostridial neurotoxin-targeting moiety, asdisclosed by Foster et al, may bind to and interfere with cells havingopioid receptors but are not involved in the pain pathway. When thisnon-specific binding and interference occur, undesirous side effects mayresult.

What is needed therefore is an specific (high affinity) therapeuticallyeffective, long duration non-cytotoxic agent and method for treatingpain.

SUMMARY

The present invention meets this need by providing specific (highaffinity) therapeutically effective, long duration non-cytotoxic agentsand methods for treating pain. I have discovered agents effective inalleviating pain, methods of making such agents and methods of usingsuch agents to alleviate pain. The present invention providesnon-cytotoxic agents for treating pain which preferably have one or moreof the characteristics of long duration of activity and specificity forthe treatment of pain with limited or substantially insignificant sideeffects at therapeutic dose levels. Furthermore, the methods ofproducing these agents are relatively straight forward and effective toprovide the desired results.

In one broad aspect of the invention, agents are provided comprising aclostridial neurotoxin or component thereof coupled to a targetingmoiety selected from the group consisting of transmission compoundsreleased from neurons in transmitting pain signals and compoundssubstantially similar to the transmission compounds.

In one preferred embodiment, the clostridial neurotoxin component iscovalently coupled to the targeting moiety. The clostridial neurotoxincomponent may, for example, be derived (i.e. made or secreted by) fromClostridial beratti, Clostridial butyricum, or Clostridial botulinum.More preferably, the clostridium neurotoxin component is derived from(that is, is made or secreted by) a Clostridial botulinum bacterium.Although it is preferable that botulinum neurotoxin type A is used,other types, for example, types B, C, D, E, F, G and mixtures thereof,may be employed.

The clostridium neurotoxin component preferably includes at least one ofa heavy chain and a light chain of a clostridial neurotoxin. Theclostridial neurotoxin component may comprise only fragments of theentire neurotoxin. For example, in one embodiment, the H_(c) of theneurotoxin is removed or modified. More preferably, the H_(c) of theneurotoxin, such as botulinum toxin type A, is removed.

In another embodiment, the L chain of a clostridial neurotoxin, or afragment of the L chain of a clostridial neurotoxin containing theendopeptidase activity, is covalently coupled to a targeting moiety. Thecovalent linkages used to couple the components of the agents mayinclude appropriate spacer regions.

In a preferred embodiment, the agent comprises the H_(N) the L chain andthe targeting moiety, covalently linked together.

The targeting moiety preferably is derived from an amino acid. In oneembodiment of the present invention, the targeting moiety is glutamate,since glutamate is recognized as a neurotransmitter that is released inthe transmission of pain signals.

In another preferred embodiment, the amino acids from which thetargeting moiety is derived link to form a peptide which is one of thepeptides released for the transmission of pain signals. For example,such peptides include neuropeptide Y, calcitonin-gene related peptide(CGRP), substance P and the like, preferably substance P.

In another embodiment, the targeting moiety can be a transmissioncompound which is, or which is substantially similar to aneurotransmitter, which is released by a neuron to initiate or topropagate the transmission of, or which facilitates the generation of, apain signal. Thus, as used herein the phrase “transmission compound”means a compound which is made by a neuron and which is secreted orreleased extracellularly (e.g. into a synaptic cleft or synaptic gap) bythe neuron. Additionally, the transmission compound is a nociceptivecompound, meaning that the transmission compound has a significantinfluence upon the generation and/or perception of pain (i.e. a “painsignal”) in response to a nociceptive event. A nociceptive event can be,for example, an inflammation, trauma, or a neuropathic syndrome. Apreferred group of transmission compounds can be selected from thetachykinin family of which substance P is a member. Examples of suchtachykinins include physalaemin, kassinin, uperolein, eledoisin, andsubstance K. Additionally, substance P precursors, fragments, analoguescomprising at least one D-amino acid and analogues comprising adisulfide bond may also be used as a targeting moiety.

In one embodiment of the present invention, the agent comprises aclostridial neurotoxin component (i.e. L-H_(N),) or parts thereof,covalently attached or coupled to substance P.

In a preferred embodiment of the present invention, the agent comprisesa botulinum neurotoxin toxin type A, or parts thereof, covalentlycoupled to substance P. In an additional preferred embodiment of thepresent invention, the agent comprises botulinum toxin neurotoxin typeA, wherein the H_(c) of the botulinum neurotoxin type A is modified,more preferably removed or deleted, and the remaining toxin (i.e. withthe H_(C) removed) is then covalently coupled to substance P.

In another embodiment of this invention, the agent comprises an L chainof a clostridial neurotoxin, or a fragment of the L chain containing theendopeptidase activity, coupled to substance P. Preferably, the L chainor fragment of the L chain is derived from botulinum toxin type A.

The agents disclose herein comprise a polypeptide, with a first andsecond amino acid sequence regions. The first region preferably includesa first domain and a second domain. Preferably, the first domaincomprises a targeting moiety, and the second domain comprises an H_(N).The targeting moiety is the same as described above. The H_(N)preferably is derived from Clostridial botulinum type A and is able tofacilitate the transfer of the entire polypeptide, or portions of thepolypeptide, preferably the second amino acid region, across anintracellular endosome membrane into the cytosol of the neuron.

The second amino acid sequence region preferably comprises the L chain.Without wishing to limit the invention to any particular theory ormechanism of operation, it is believed that the L chain is an effectivetherapeutic element having biological activity because, as discussedabove, once it is translocated inside the neuron it interferes with theexocytosis process of a neurotransmitter.

In another broad aspect of this invention, the present agents areexpressed recombinantly with the targeting moiety, as a fusion proteintherefore.

In one embodiment, recombinant techniques are used to produce theclostridial neurotoxin components of the present agents. The techniqueincludes generating genetic constructs which have codes for clostridialneurotoxins, modified clostridial neurotoxins, or fragments thereof. Thegenetic constructs are then fused with cloning vectors, such asplasmids, and are incorporated into a host cell for amplification. Theexpressed clostridial components can then isolated by conventional andknown techniques.

A clostridial neurotoxin expressed recombinantly without a targetingmoiety can be chemically coupled to a targeting moiety (conjugateformation). Preferably, the linkages between the clostridial componentsand the targeting moieties include appropriate spacer regions.

In another embodiment, the genetic constructs include genes coding forboth the clostridial neurotoxin components and the targeting moieties.Additionally, the genetic constructs may include genes coding forappropriate spacer regions between the clostridial neurotoxin componentsand the targeting moieties.

In another broad aspect of this invention, there are provided methodsfor treatment of pain which comprise administering effective doses ofthe agents according to the invention. The routes of administrationpreferably include administration locally to the spine and locally tothe peripheral location of pain.

In one embodiment, the present agents in therapeutically effectiveamounts, for example, between about 1 U and about 500 U, can beadministered, for example, intraspinally administered, to alleviate painexperienced by a mammal. Preferably the amounts are between about 10 Uand about 300 U. More preferably the amount is between about 20 and 250units, such about 50 U to 200 U or 70 U.

In a human patient, the therapeutically effective doses (for agentsderived from botulinum toxin type A) are in the amounts between about10⁻³ U/kg and about 35 U/kg. Preferably, the agents used areadministered in amounts between about 1 U/kg and about 10 U/kg. Morepreferably, the agents are administered in amounts of about 3 U/kg.Significantly, the pain alleviating effect of the present agents canpersist for between about 2-6 months per administration.

The intraspinal administrations of the agents are preferably byintrathecal administration, such as intrathecally to a cranial,cervical, thoracic, lumbar, sacral or coccygeal region of the centralnervous system and the administration step can include the steps ofaccessing a subarachnoid space of the central nervous system of themammal, and injecting the agents into the subarachnoid space. Theaccessing step can be carried out by affecting a spinal tap.

Alternately, the intraspinal administration step can include the stepsof catheterization of a subarachnoid space of the central nervous systemof the mammal, followed by injection of the agents through a catheterinserted by the catheterization step into the subarachnoid space. Notethat prior to the injecting step there can be the step of attaching toor implanting in the mammal an administration means for administeringthe agents to the central nervous system of the mammal. Theadministration means can be made up of a reservoir of the agents, wherethe reservoir is operably connected to a pump means for pumping analiquot of the agents out of the reservoir and into an end of thecatheter in the subarachnoid space.

Each and every feature described herein, and each and every combinationof two or more of such features, is included within the scope of thepresent invention provided that the features included in such acombination are not mutually inconsistent.

Definitions

Light chain means the light chain of a clostridial neurotoxin. It has amolecular weight of about 50 kDa, and can be referred to as L chain, Lor as the proteolytic domain (amino acid sequence) of a clostridialneurotoxin.

Heavy chain means the heavy chain of a clostridial neurotoxin. It has amolecular weight of about 100 kDa and can be referred to as H chain oras H.

H_(c) means a fragment (about 50 kDa) derived from the H chain of aclostridial neurotoxin which is approximately equivalent to the carboxylend segment of the H chain, or the portion corresponding to thatfragment in the intact H chain. It is believed to be immunogenic and tocontain the portion of the natural or wild type clostridial neurotoxininvolved in high affinity, presynaptic binding to motor neurons.

H_(N) means a fragment (about 50 kDa) derived from the H chain of aclostridial neurotoxin which is approximately equivalent to the aminoend segment of the H chain, or the portion corresponding to thatfragment in the intact in the H chain. It is believed to contains theportion of the natural or wild type clostridial neurotoxin involved inthe translocation of the L chain across an intracellular endosomalmembrane.

LH_(N) or L-H_(N) means a fragment derived from a clostridial neurotoxinthat contains the L chain, or a functional fragment thereof coupled tothe H_(N) domain It can be obtained from the intact clostridialneurotoxin by proteolysis, so as to remove or to modify the H_(C)domain.

Targeting moiety means a molecule that has a specific binding affinityfor a cell surface receptor, for example, for a neuronal receptor so asto influence the transmission or reception of pain signals by theneuron.

Importantly, the agents disclosed herein are preferably administered bylocal administration, that is directly to the site where a therapeuticeffect is desired.

DESCRIPTION

This invention is based upon the discovery that pain can be treated byadministration to a patient of an agent which is comprised of aderivative of a clostridial neurotoxin and a targeting moiety, where thetargeting moiety is selected from the group consisting of transmissioncompounds which can be released from a neuron upon the initiation,transmission of, or facilitation of the generation of, a pain signal bythe neuron.

Significantly, the agents of the present invention can alleviate painwithout being cytotoxic to their target neurons. Furthermore, agentswithin the scope of the present invention can be administered to bothcentral nociceptive neurons and to primary sensory afferent neurons

The mechanism of action for these agents in alleviating pain iscurrently not fully understood. Without wishing to limit the inventionto any particular theory or mechanism of operation, it is believed that,at least with respect to areas in spinal cord, the agents disclosedherein target neurons having receptors for neurotransmitters that arereleased by neurons for or upon the transmission of pain signals. Forexample, when the targeting moiety is substance P, the agent is thoughtto interact with neurons expressing substance P receptors (SPR), such asprojection neurons. Moreover, the receptors binding neurotransmittersreleased for the transmission of pain are primarily expressed on cellsinvolved in the transmission of pain signals. For example, with respectto the central nervous system, it is well known that substance Preceptors are primarily expressed on projection neurons in the dorsalhorn of the spinal cord. See e.g. Vigna et al, J. Neuroscience,14(2):834-845 (1994).

Therefore, the agents as described in this invention preferably are veryspecific for treating pain because they do not substantially orsignificantly interact and/or interfere with neurons and cells of othersystems. Moreover, it is believed that the agents of this invention mayenter into these specific neurons, for example projection neurons,through an endocytosis process. Once inside the neurons, it is furtherbelieved that the H_(N) of these agents facilitate the translocation ofthe agent into the cytosol. In the cytosol, the agent, or a componentthereof, can inhibit the release of a neurotransmitter involved in thefurther transmission of pain signals. It is further believed that the Lchain of the clostridial neurotoxin component of the agent isresponsible for the inhibition of the release of neurotransmitters thatare involved in pain transmission by interfering with their vesicularexocytosis.

Additionally, the agents of this invention also provide pain alleviatingeffects when locally applied to peripheral pain sites. Also withoutwishing to limit the invention to any particular theory or mechanism ofoperation, it is believed that the agents interfere with the functionsof cells having receptors for nociception, for example orphanin,substance P and/or kyotorphin, at the peripheral locations. See Ueda,Jpn J. Pharmacology, 79(3):263-268, the content of which is incorporatedin its entirety herein by reference. These cells are uniquely involvedin pain transmissions and the disruption of their functions by theagents can result in pain alleviation. Furthermore, it is believed thatthe mechanism for the inhibitory effects by agents in these cells issimilar to that described above. Moreover, these agents can also bind,enter into and interfere with the function of primary sensory neurons.

According to one broad aspect of the invention, the clostridialneurotoxin component is covalently coupled to a targeting moiety. Theclostridial neurotoxin component is a polypeptide and may be derivedfrom Clostridial beratti, Clostridial butyricum, or Clostridialbotulinum. More preferably, the clostridium neurotoxin component isderived from Clostridial botulinum. Clostridial botulinum producesbotulinum toxin types A, B, C, D, E, F and G. Although any of thesetoxin types may be used in the present invention, botulinum type A ismore preferably used.

Furthermore, the clostridial neurotoxin component may comprises only afragment of the entire neurotoxin. For example, it is known in the artthat the H_(c) of the neurotoxin molecule can be removed from the othersegment of the H chain, the H_(N), such that the H_(N) fragment remainsdisulphide linked to the L chain of the neurotoxin molecule to provide afragment known as known as the LH_(N). Thus, in one embodiment of thepresent invention the LH_(N) fragment of a clostridial neurotoxin iscovalently coupled, using linkages which may include one or more spacerregions, to a targeting moiety.

In another embodiment of the invention, the domain having the H_(c) of aclostridial neurotoxin is removed, mutated or modified, e.g. by chemicalmodification, to reduce, or preferably incapacitate, its ability to bindthe neurotoxin to receptors at the neuromuscular junction. This modifiedclostridial neurotoxin is then covalently coupled, using linkages whichmay include one or more spacer regions, to a targeting moiety.

In another embodiment of the invention, the H chain of a clostridialneurotoxin, in which the H_(c) is removed, mutated or modified, e.g. bychemical modification, to reduce, preferably incapacitate, its abilityto bind the neurotoxin to receptors at the neuromuscular junction iscombined with the L-chain of a different clostridial neurotoxin, to forma hybrid. For example, in one embodiment, the clostridial neurotoxincomponent comprises an H chain with the H_(c) removed, mutated ormodified derived from botulinum toxin type A, and an L chain derivedfrom another botulinum toxin type. The described hybrid is covalentlycoupled to a targeting moiety, preferably with one or more spacerregions.

In another embodiment of the invention the L chain of a clostridialneurotoxin, or a fragment of the L chain containing the endopeptidaseactivity, is linked, using linkages which may include one or more spacerregions, to a targeting moiety which can also effect the internalizationof the L chain, or fragment thereof containing endopeptidase activity,into the cytoplasm of the cell.

In a preferred embodiment, the agent comprises the H_(N) the L chain andthe targeting moiety, covalently linked together. The targeting moietyaccording to the first aspect of the invention is preferably derivedfrom amino acids, substituted counterparts thereof and mixtures thereof.The term “substituted counterparts thereof” as it relates to any of theabove noted amino acids refers to molecules that are functionally andphysically similar to the amino acids, either as independent units orunits incorporated into macromolecules, for example, peptides.

In one preferred aspect of the present invention, the targeting moietyis glutamate, since glutamate is the predominant neurotransmitter at thesynapses between primary afferents and projection neurons. In anotherembodiment, the targeting moieties may be components that aresubstantially similar to the transmission compounds, for example,glutamate, in this particular instance. Hereinafter, the term“components that are substantially similar to the transmissioncompounds,” is defined as molecules or substances that have the samefunctions as that of the transmission compounds, for example, binding toreceptors that are involved in the transmission of pain signals.

In one embodiment, components that are substantially similar toglutamate are agonists of glutamate. For example, componentssubstantially similar to glutamate are quisqualate,DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate,N-Me-D-aspartate, kinate and the like. Additionally, componentssubstantially similar to glutamate may also include antagonists ofglutamate. For example, these molecules include6-cyano-7nitroquinozaline-2,3-dione,3-(2-carboxypiperazin-4-yl)propyl-1-phosponic acid, lactonized kainateand the like.

In a more preferred embodiment, the amino acids link to form one of thepeptides which are released by neurons for the transmission of painsignals. For example, these peptides include neuropeptide Y andcalcitonin-gene related peptide (CGRP). Even more preferably, thepeptide is substance P.

In another embodiment, components substantially similar to substance Pmay be used as targeting moieties. These components include substance Pprecursors, fragments, analogs and/or derivatives. The history,isolation, identification, and synthesis of substance P and itsprecursors, fragments, analogs and/or derivatives are disclosed in U.S.Pat. No. 5,891,842 (incorporated herein by reference in its entirety)

Substance P is an 11 amino acid peptide which has a number of differentnatural and synthetic precursor forms; has been demonstrated to beconverted into a variety of naturally occurring amino-terminal peptidefragments; and can be obtained in analog format compromising,substituted counterparts thereof, for example, lysine methyl ester,D-amino acids or disulfide bridges substitutions, thereby yielding morestable and discriminating formulations. A representative listing ofsubstance P and its related chemical entities is provided by Table 1below. The amino acid sequence (1) in Table 1(Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-amide) can be referred to aSEQ ID NO:1, and the subsequent 17 amino acid sequences set forth inTable one can be similarly identified as SEQ ID NO:2 to SEQ ID NO:18.

The components substantially similar to substance P may also includemolecules in the same family as that of substance P. For example, apreferred family of such molecules would be the tachykinin family towhich substance P is a member. Examples of some family members oftachykinins include physalaemin, kassinin, uperolein, eledoisin,substance K and the like.

In a preferred embodiment, the agent comprises a clostridial neurotoxincomponent, for example LH_(N), coupled to substance P. In anotherpreferred embodiment, the agent comprises a hybrid of two clostridialneurotoxins, such as the H chain, preferably H_(N), derived frombotulinum toxin A and the L chain derived from another botulinum toxin,coupled to substance P. In another preferred embodiment, the clostridialcomponent of the agent is a botulinum toxin type A in which the H_(c)has been removed or modified, coupled to substance P.

In another preferred embodiment, the agent comprises an L chain of aclostridial neurotoxin, or a fragment of the L chain containing theendopeptidase activity, coupled substance P. Even more preferably, the Lchain or fragment of the L chain is derived from botulinum toxin A, andis coupled to substance P. Additionally, it is preferred that the Lchain coupled to the substance P is covalently linked to H_(N).

The clostridial components and the targeting moieties are coupled bycovalent linkages. In a preferred embodiment, the linkages may includeappropriate spacer regions. Spacer regions have many functions withinthis invention. For example, one of the functions of the spacer regionsis to provide for adequate distance between the clostridial neurotoxincomponents and the targeting moieties so that the two components canindependently and freely move about, without an internal sterichindrance.

In one embodiment, the spacer region is made up of sugar molecules, forexample, saccharides, glucose, etc. In another embodiment, the spacerregion may be constructed from a an aliphatic chain. In anotherembodiment, the spacer regions may be constructed by linking together aseries of amino acids, preferably glycine because they are small and aredevoid of any functional group. In yet another embodiment, the spacerregion may comprise one or more of the sugar molecules, aliphaticchains, and amino acids.

Also, these agents can be thought of as being polypeptides, with a firstand a second amino acid sequence region. The first region preferablyincludes a first domain and a second domain. Preferably, the firstdomain of the first amino acid sequence comprises a targeting moiety. Inone embodiment, the targeting moiety is able to bind to surfacereceptors of the spinal cord neurons under physiological conditions.More preferably, the targeting moiety specifically binds a receptor on aspinal cord dorsal horn neuron, for example a projection neuron.

Preferably, the second domain comprises a heavy chain or a portionthereof of a clostridial neurotoxin. Even more preferably, the H_(N) ofthe heavy chain is able to facilitate the transfer of the polypeptideacross an endosome membrane into the cytosol of the neuron. In oneembodiment, the second domain of the first amino acid sequence comprisesa clostridial neurotoxin heavy chain. More preferably, the clostridialneurotoxin heavy chain is derived from Clostridium botulinum neurotoxintype A. Even more preferably, the heavy chain is derived from the H_(N)of Clostridium botulinum neurotoxin type A. In yet another embodiment,the heavy chain may be derived from Clostridial botulinum types B, C, D,E, F, G and mixtures thereof. Also, the heavy chain may be derived fromClostridial baratii and Clostridial butyricum. Additionally, the heavychain, preferably the H_(N), may be derived from Clostridial tetani.

The second amino acid sequence region preferably comprises the L chain.The L chain is the effective therapeutic element having biologicalactivity because, as discussed above, once it is transferred inside theneuron it interferes with the exocytosis process of neurotransmitter.Preferably, the light chain is derived from Clostridial botulinumneurotoxin type A. According to another broad aspect of this inventionrecombinant techniques are used to produce the clostridial neurotoxincomponents of the agents. The technique includes steps of obtaininggenetic materials from either DNA cloned from natural sources, orsynthetic oligonucleotide sequences, which have codes for clostridialneurotoxin components including clostridial neurotoxins, modifiedclostridial neurotoxins and fragments thereof. The genetic constructsare incorporated into host cells for amplification by first fusing thegenetic constructs with a cloning vectors, such as phages or plasmids.Then the cloning vectors are inserted into hosts, preferably E. coli's.Following the expressions of the recombinant genes in host cells, theresultant proteins can be isolated using conventional techniques. Theclostridial neurotoxin components derived from the recombinanttechniques can then be chemically coupled to targeting moieties.Preferably, the linkages between the clostridial components and thetargeting moieties include an appropriate spacer regions.

In another embodiment, the genetic constructs include genes coding forboth the clostridial neurotoxin components and the targeting moieties,for example, forming fusion proteins. Additionally, the geneticconstructs may include genes coding for appropriate spacer regionsbetween the clostridial neurotoxin components and the targetingmoieties. From this aspect, the agents may be thought of as polypeptidescomprising a first amino acid sequence region and a second amino acidsequence region. The first region may further comprise a first domainand a second domain. The details of these regions and domains aredescribed above.

In another embodiment, the required L-H_(N), which may be a hybrid of anL chain and an H_(N) from different clostridial toxin types, isexpressed recombinantly as a fusion protein. Such LH_(N) hybrid may alsobe coupled to the targeting moiety, which may further include one ormore spacer regions between them.

In another embodiment of the invention the L chain of a clostridialneurotoxin, or a fragment of the L chain containing the endopeptidaseactivity, is expressed recombinantly as a fusion protein with the H_(N)of the H chain and the targeting moiety which can also affect theinternalization of the L chain, or fragment thereof containing theendopeptidase activity, into the cytoplasm of the cell. The expressedfusion protein may also include one or more spacer regions.

There are many advantages to producing these agents recombinantly. Forexample, production of neurotoxin from anaerobic Clostridium cultures isa cumbersome and time-consuming process including a multi-steppurification protocol involving several protein precipitation steps andeither prolonged and repeated crystallization of the toxin or severalstages of column chromatography. Significantly, the high toxicity of theproduct dictates that the procedure must be performed under strictcontainment (BL-3). During the fermentation process, the foldedsingle-chain neurotoxins are activated by endogenous clostridialproteases through a process termed nicking. This involves the removal ofapproximately 10 amino acid residues from the single-chain to create thedichain form in which the two chains remain covalently linked throughthe intrachain disulfide bond.

The nicked neurotoxin is much more active than the unnicked form. Theamount and precise location of nicking varies with the serotypes of thebacteria producing the toxin. The differences in single-chain neurotoxinactivation and, hence, the yield of nicked toxin, are due to variationsin the type and amounts of proteolytic activity produced by a givenstrain. For example, greater than 99% of Clostridial botulinum type Asingle-chain neurotoxin is activated by the Hall A Clostridial botulinumstrain, whereas type B and E strains produce toxins with lower amountsof activation (0 to 75% depending upon the fermentation time). Thus, thehigh toxicity of the mature neurotoxin plays a major part in thecommercial manufacture of neurotoxins as therapeutic agents.

The degree of activation of engineered clostridial toxins is, therefore,an important consideration for manufacture of these materials. It wouldbe a major advantage if neurotoxins such as botulinum toxin and tetanustoxin could be expressed, recombinantly, in high yield inrapidly-growing bacteria (such as heterologous E. coli cells) asrelatively non-toxic single-chains (or single chains having reducedtoxic activity) which are safe, easy to isolate and simple to convert tothe fully-active form.

With safety being a prime concern, previous work has concentrated on theexpression in E. coli and purification of individual H and L chains oftetanus and botulinum toxins; these isolated chains are, by themselves,non-toxic; see Li et al., Biochemistry 33:7014-7020 (1994); Zhou et al.,Biochemistry 34:15175-15181 (1995), hereby incorporated by referenceherein. Following the separate production of these peptide chains andunder strictly controlled conditions the H and L subunits can becombined by oxidative disulphide linkage to form the neuroparalyticdi-chains.

In another broad aspect of this invention, methods are provided for thetreatment of pain which comprise administering effective doses of theagents according to the invention. The agents described in thisinvention can be used in vivo, either directly formulated or as apharmaceutically acceptable salt, for treatment of pain.

For example, in a preferable embodiment, agents according to theinvention can be administered by spinal injection (epidural orintrathecal) at the level of the spinal segment involved in theinnervation of an affected organ for the treatment of pain. This is, forexample, applicable in the treatment of deep tissue pain, such aschronic malignant pain.

As used herein “intraspinal” means into or within the epidural space,the intrathecal space, the white or gray matter of the spinal cord oraffiliated structures such as the dorsal root and dorsal root ganglia.

Preferably, clostridial neurotoxin components of agents used to practicea method within the scope of the present invention comprise botulinumtoxins, such as one of the type A, B, C, D, E, F or G. Preferably, thebotulinum toxin used is botulinum toxin type A, because of its highpotency in humans and ready availability. The targeting moiety of theagents used to practice the method herein is preferably a substance P.

An intraspinal route for administration of a neurotoxin according to thepresent disclosed invention can be selected based upon criteria such asthe solubility characteristics of the agents chosen as well as theamount of the agents to be administered. The amount of the agentsadministered can vary widely according to the particular disorder beingtreated, its severity and other various patient variables includingsize, weight, age, and responsiveness to therapy. For example, theextent of the area of CNS afferent pain neuron somata influenced isbelieved to be proportional to the volume of agents injected, while thequantity of the analgesia is, for most dose ranges, believed to beproportional to the concentration of agents injected. Furthermore, theparticular intraspinal location for agents administration can dependupon the dermosome location of the pain to be treated. Methods fordetermining the appropriate route of administration and dosage aregenerally determined on a case by case basis by the attending physician.Such determinations are routine to one of ordinary skill in the art (seefor example, Harrison's Principles of Internal Medicine (1998), editedby Anthony Fauci et al., 14^(th) edition, published by McGraw Hill).

Preferably, the intraspinal administration is carried out intrathecallybecause of the greater ease in which the relatively larger intrathecalspace is accessed and because the preferred agents generally exhibitslow solubility in the lipid rich epidural environment. It is found thatboth inflammatory and neuropathic pain can be effectively treated by thedisclosed methods without significant muscle spasticity or flaccidity orother side effects.

Intraspinal administration of the agents according to the presentinvention can be by various routes such as by catheterization or byspinal tap injection. The long lasting nature of the therapeutic effectsof the present invention substantially removes the need for chronicantinociceptive drug administration, so that the present methods areadvantageously practiced by infrequent spinal tap injection of theagents. Additionally, an intrathecal spinal tap agents administrationroute facilitates a more precise and localized delivery of agents withless danger of damage to the CNS, as compared to moving a catheter toaccess other CNS locations.

Intrathecal agents can be administered by bolus injection or bycatheterization. The catheter can be inserted at L3-4 or at L4-5, a safedistance from the spinal cord which in humans terminates at L1, andguided upward in the subarachnoid space to rest at the desired site. Forpain management, placement of the catheter or location of bolusinjection by syringe depends on the site of the perceived pain, and thephysicians preference. It is important to note that therapeutic agentadministration according to the present disclosed methods can be carriedout before the occurrence of or during the experience of a nociceptiveevent or syndrome.

It is found that an agent, such as the LH_(N) (derived from botulinumtoxin type A)-substance P, can be intraspinally administered accordingto the present disclosed methods in amounts between about 1 U to about500 U. Preferably the amounts are between about 10 U and about 300 U.More preferably the amount is between about 10 and about 200 U, such asabout 70 U.

In a human patient, the therapeutically effective doses (when theclostridial neurotoxin component is derived from a botulinum toxin typeA) can be amounts between about 10⁻³ U/kg and about 35 U/kg. A dose ofabout 10⁻³ U/kg can result in an antinociceptive effect if delivereddirectly to or onto the dorsal horn of the CNS and/or if agents deliveryis assisted by methods such as iontophoresis. Intraspinal administrationof less than about 10⁻³ U/kg does not result in a significant or lastingtherapeutic result. An intraspinal dose of more than 35 U/kg approachesa lethal dose of an agent such as the L-H_(N) (derived from botulinumtoxin type A)-substance P. It is desired that the agents used to obtaineither antinociceptive effect contact the nerves of the CNS so as tofavorably influence or down regulate the perception of pain in theinnervated organ or tissue. Thus, intraspinal administration of agentsby, for example, epidural injection can require an increase of thedosage by a factor of about ten to account for dilution of the agentsupon diffusion from the epidural space to the intrathecal space andthence to the exterior nerves of the CNS.

A preferred range for intrathecal administration of an agent, such asthe LH_(N)(type A)-substance P, so as to achieve an antinociceptiveeffect in the patient treated is from about 10⁻² U/kg to about 10 U/kg.A more preferred range for intrathecal administration of an agent, suchas the LH_(N) (derived from botulinum toxin type A)-substance P, so asto achieve an antinociceptive effect in the patient treated is fromabout 10⁻¹ U/kg to about 10 U/kg. Less than about 10⁻¹ U/kg can resultin the desired therapeutic effect being of less than the optimal orlongest possible duration, while more than about 10 U/kg can stillresult in some symptoms of muscle flaccidity. A most preferred range forintrathecal administration of an agent, such as the L-H_(N) (derivedfrom botulinum toxin type A)-substance P, so as to achieve anantinociceptive effect in the patient treated is from about 1 U/kg toabout 10 U/kg. Intrathecal administration of an agent, such as theL-H_(N) (derived from botulinum toxin type A)-substance P, in thispreferred range can provide dramatic therapeutic success. Furthermore,our experimental work indicates that a dose of about 3 U/kg can providesignificant and long lasting antinociceptive effect without significantside effects for the treatment of inflammatory and neuropathic pain inhuman patients.

Although intraspinal administration of the agents is preferred for thetreatment of pain, other routes of administration are possible. Forexample, the agent according to the invention can also be locallyapplied to a peripheral site of pain to alleviate such pain. A specificexample of this is treatment by local application of the agents into ajoint affected by inflammatory pain. Another example is treatment ofmuscular pain by subcutaneous, preferably intramuscular, injection ofthe agents into the location of pain.

The present invention includes within its scope the use of any agentwhich has a long duration antinociceptive effect when applied centrallyor peripherally into a patient. For example, agents having theclostridial neurotoxin components made by any of the species of thetoxin producing Clostridium bacteria, such as Clostridium botulinum,Clostridium butyricum, Clostridium beratti and Clostridium tetani can beused or adapted for use in the methods of the present invention.Additionally, all of the botulinum serotypes A, B, C, D, E, F and G canbe advantageously used in the practice of the present invention,although type A is the most preferred and type B the least preferred, asexplained above. Practice of the present invention can provide ananalgesic effect, per injection, for 2 months or longer, for example 6months, in humans.

EXAMPLES

The following examples provide those of ordinary skill in the art withspecific preferred methods to produce the agents, example 1, and totreat pain, examples 2 through 8, within the scope of the presentinvention and are not intended to limit the scope of the invention.

Example 1 Recombinant Production of Agents

The production of a fusion of L-H_(N) whereof the L chain is derivedfrom botulinum toxin type B and the amine end segment of the H chainfragment is derived from botulinum toxin type A. The H_(N) fragment ofthe botulinum toxin type A is produced according to the method describedby Shone C. C., Hambleton, P., and Melling, J. (1987, Eur. J. Biochem.167, 175-180) and the L chain of botulinum toxin type B according to themethod of Sathyamoorthy, V. and DasGupta, B. R. (1985, J. Biol. Chem.260, 10461-10466). The free cysteine on the amine end segment of the Hchain fragment of botulinum toxin type A is then derivatized by theaddition of a ten-fold molar excess of dipyridyl disulphide followed byincubation at 4 degree C. overnight. The excess dipyridyl disulphide andthe thiopyridone by product are then removed by desalting the proteinover a PD10 column (Pharmacia) into PBS.

The derivatized H_(N) is then concentrated to a protein concentration inexcess of 1 mg/ml before being mixed with an equimolar portion of Lchain from botulinum toxin type B (>1 mg/ml in PBS). After overnightincubation at room temperature the mixture is separated by sizeexclusion chromatography over Superose 6 (Pharmacia), and the fractionsanalyzed by SDS-PAGE. The chimeric LH_(N) is then available fordramatization to produce a targeted conjugate.

The example described above is purely illustrative of the invention. Insynthesizing the agents, the coupling of the targeting moieties to theclostridial components, for example the modified clostridial neurotoxinsor fragments thereof, is achieved via chemical coupling using reagentsand techniques known to those skilled in the art. Thus, although theexamples given use exclusively the PDPH/EDAC and Traut's reagentchemistry any other coupling chemistry capable of covalently attachingthe targeting moieties of the agents to clostridial neurotoxincomponents and known to those skilled in the art is covered by the scopeof this application. Similarly it is evident to those skilled in the artthat either the DNA coding for either the entire composition of theagents or fragments of the agents could be readily constructed and, whenexpressed in an appropriate organism, could be used to recombinantlyproduce the agents or fragments of the agents. Such genetic constructsof the agents of the invention obtained by techniques known to thoseskilled in the art are also covered in the scope of this invention.

Example 2 Treatment of Inflammatory Pain by Intrathecal Administrationof an Agent

A patient, age 45, experiencing acute inflammatory pain is treated byintrathecal administration, for example by spinal tap to the lumbarregion, with between about 0.1 U/kg and 30 U/kg, (preferably from 20 Uto 500 U), of an agent comprising an L-H_(N) (derived from botulinumtoxin type A)-substance P, the particular agent dose and site ofinjection, as well as the frequency of agent administrations depend upona variety of factors within the skill of the treating physician, aspreviously set forth. Within 1-7 days after agent administration thepatient's pain is substantially alleviated. The duration of painreduction is from about 2 to about 6 months.

The agent can be injected at different spinal levels to treat differentdermosomes, that is to treat pain in various body parts. Additionally, acatheter can be percutaneously inserted into the intrathecal space vialumbar puncture at vertebral level L3-4 or L4-5 using a Tuohy needle.When CSF flow is discernible a silastic catheter is threaded cephaladusing a C-arm for verification of catheter placement. The catheter canbe advanced to different vertebral locations and/or used at differentdose concentrations to treat different types of pain and/or spasm. Thus,the catheter can be placed within the intrathecal space at thedermasomal level of the pain or spasm experienced.

Example 3 Treatment of Neuropathic Pain by Intrathecal Administration ofan Agent

A patient, age 36, experiencing pain of neuropathic origin is treated byintrathecal administration through spinal tap to the lumbar region ofbetween about 0.1 U/kg and 30 U/kg, (preferably from 20 U to 500 U), ofan agent comprising an L-H_(N) (derived from botulinum toxin typeA)-substance P. Within 1-7 days the pain symptoms are substantiallyalleviated. The duration of pain reduction is from about 2 to about 6months.

Example 4 Treatment of Pain Subsequent to Spinal Cord Injury byIntrathecal Administration of an Agent

A patient, age 39, experiencing pain subsequent to spinal cord injury istreated by intrathecal administration, for example by spinal tap or bycatheterization, to the spinal cord, such as to the lumbar region of thespinal cord, with between about 01 U/kg and 20 U/kg, (preferably between20 U to 500 U), of an agent comprising an L-H_(N) (derived frombotulinum toxin type A)-substance P, the particular dose and site ofinjection, as well as the frequency of administrations depend upon avariety of factors within the skill of the treating physician, aspreviously set forth. Within 1-7 days after administration of the agentthe patient's pain is substantially alleviated. The duration of painreduction is from about 2 to about 6 months.

Example 5 Treatment of Pain Subsequent to Limb Injury by IntrathecalAdministration of an Agent

A patient, age 51, experiencing pain subsequent to injury to his hand,arm, foot or leg is treated by intrathecal administration, for exampleby spinal tap or by catheterization, to the spinal cord, such as to thelumbar region of the spinal cord, with between about 01 U/kg and 20U/kg, (preferably from 20 U to 500 U), of an agent comprising L-H_(N)(derived from botulinum neurotoxin type A)-substance P, the particulardose and site of injection, as well as the frequency of administrationsdepend upon a variety of factors within the skill of the treatingphysician, as previously set forth. Within 1-7 days after administrationthe patient's pain is substantially alleviated. The duration of painreduction is from about 2 to about 6 months.

Example 6 Treatment of Pain Associated with Cancer by IntrathecalAdministration of an Agent

A patient, age 63, suffering from pain associated with cancer is treatedby intrathecal administration, for example by spinal tap or bycatheterization, to the spinal cord, such as to the lumbar region of thespinal cord, with between about 1 U/kg and 20 U/kg (preferably about 20U to 500 U), of an agent comprising an LH_(N) (derived from botulinumneurotoxin type A)-substance P, the particular dose and site ofinjection, as well as the frequency of administrations depend upon avariety of factors within the skill of the treating physician, aspreviously set forth. Within 1-7 days after administration the patient'spain is substantially alleviated. The duration of pain reduction is fromabout 2 to about 6 months.

Example 7 Treatment of Pain Associated with Diabetes by IntrathecalAdministration of an Agent

A patient, age 47, suffering from pain associated with diabetes istreated by intrathecal administration, for example by spinal tap or bycatheterization, to the spinal cord, such as to the lumbar region of thespinal cord, with between about 0.1 U/kg and 30 U/kg, or 1 to 500 U, ofan agent comprising an L-H_(N) (derived from a botulinum neurotoxin typeA)-substance P, the particular dose and site of injection, as well asthe frequency of administrations depend upon a variety of factors withinthe skill of the treating physician, as previously set forth. Within 1-7days after administration the patient's pain is substantiallyalleviated. The duration of pain reduction is from about 2 to about 6months.

Example 8 Treatment of Pain Subsequent to Limb Injury by PeripheralAdministration of an Agent

A patient, age 35, experiencing pain subsequent to injury to his hand,arm, foot or leg is treated by intramuscular injection with betweenabout 1 U/kg and 20 U/kg (preferably from 20 U to 500 U), of an agentcomprising L-H_(N) (derived from a botulinum neurotoxin typeA)-substance P. The particular dose and site of injection, as well asthe frequency of administrations depend upon a variety of factors withinthe skill of the treating physician, as previously set forth. Within 1-7days after administration the patient's pain is substantiallyalleviated. The duration of pain reduction is from about 2 to about 6months.

Although the present invention has been described in detail with regardto certain preferred methods, other embodiments, versions, andmodifications within the scope of the present invention are possible.For example, a wide variety of neurotoxins can be effectively used inthe methods of the present invention in place of clostridialneurotoxins. Additionally, the present invention includes intraspinaladministration methods wherein two or more agents, such as two or moreagents comprising different clostridial toxin components and targetingmoieties, are administered concurrently or consecutively. For example,an agent comprising a an LH_(N) (botulinum neurotoxin type A)-substanceP can be administered intraspinally until a loss of clinical response orneutralizing antibodies develop, followed by administration of an agentcomprising L-H_(N) (derived from a botulinum neurotoxin typeE)-substance P. While this invention has been described with respect tovarious specific examples and embodiments, it is to be understood thatthe invention is not limited thereto and that it can be variouslypracticed with the scope of the following claims.

1. A method for treating pain in a patient, the method comprising thestep of administering a therapeutically effective amount of a modifiedClostridial toxin to the patient; wherein the modified Clostridial toxincomprises a Clostridial toxin proteolytic domain; a Clostridial toxintranslocation domain and an orphanin targeting moiety; and wherein theClostridial toxin binding domain of the modified Clostridial toxin isremoved or modified in order to reduce the targeting of the modifiedClostridial toxin to the neuromuscular junction.
 2. The method accordingto claim 1, wherein the Clostridial toxin proteolytic domain comprises abotulinum toxin proteolytic domain.
 3. The method according to claim 2,wherein the botulinum toxin proteolytic domain is selected from thegroup consisting of a botulinum toxin serotype A proteolytic domain, abotulinum toxin serotype B proteolytic domain, a botulinum toxinserotype C1 proteolytic domain, a botulinum toxin serotype D proteolyticdomain, a botulinum toxin serotype E proteolytic domain, a botulinumtoxin serotype F proteolytic domain and a botulinum toxin serotype Gproteolytic domain.
 4. The method according to claim 1, wherein theClostridial toxin translocation domain comprises a botulinum toxintranslocation domain.
 5. The method according to claim 4, wherein thebotulinum toxin translocation domain is selected from the groupconsisting of a botulinum toxin serotype A translocation domain, abotulinum toxin serotype B translocation domain, a botulinum toxinserotype C1 translocation domain, a botulinum toxin serotype Dtranslocation domain, a botulinum toxin serotype E translocation domain,a botulinum toxin serotype F translocation domain and a botulinum toxinserotype G translocation domain.
 6. The method according to claim 1,wherein the modified Clostridial toxin is administered locally at theperiphery.
 7. The method according to claim 1, wherein the modifiedClostridial toxin is administered intramuscularly.
 8. The methodaccording to claim 1, wherein the modified Clostridial toxin isadministered intrathecally.
 9. The method according to claim 1, whereinthe pain treatment persists for about two months to about six months.10. The method according to claim 1, wherein the pain treatment iscarried out prior to an onset of a pain event or syndrome experienced bythe patient.
 11. The method according to claim 1, wherein the paintreatment is carried out after an onset of a pain event or syndromeexperienced by the patient.
 12. The method according to claim 1, whereinthe pain treatment is for an inflammatory pain.
 13. The method accordingto claim 1, wherein the pain treatment is for a neuropathic pain. 14.The method according to claim 1, wherein the effect of the paintreatment persists for at least two months.
 15. The method according toclaim 1, wherein the pain treatment reduces pain by at least 20%. 16.The method according to claim 1, wherein the pain treatment reduces painby at least 50%.
 17. The method according to claim 1, wherein the paintreatment reduces pain by at least 80%.